A. Field of the Invention
The present invention relates to percussion musical instruments, particularly drums and drumheads and, specifically to a portable electronic drumhead which is uniformly responsive to barely audible drumstick impacts over its entire upper surface in producing electronic signals which are clearly audible in earphones as realistic simulations of percussion drumhead impact sounds.
B. Description of Background Art
A variety of acoustic drums have long been used by orchestras, bands and other musical groups. Drum types commonly used by musicians include kettle drums, also known as tympani, base or kick drums, snare drums and tomtoms. All acoustic drums include a drum head at one or both ends of a hollow cylindrical shell. The drumheads usually consist of a thin membrane made from an animal skin or synthetic polymer. The membrane is held in tension over the open end of the shell, and the outer surface of the membrane is used as a striking or batter surface which is struck by drumstick, mallet fingers or hand, causing the drumhead on an air column within the shell to vibrate at audible frequencies.
For various reasons, traditional acoustic drums are sometimes supplemented with or replaced by electronic devices. Thus, for some applications, the sounds produced by even small drums are too loud for the particular acoustic environment, and/or a particular event. In such cases, acoustic drums are sometimes fitted with passive sound attenuating accessories such as batter pads, and one or more electronic transducers which convert the sound vibrations of the drum produced by a drumstick impacting a drumhead into electronic signals. These signals are then input to an electronic signal processing device which amplifies or attenuates the drumhead vibrations to adjustable volume-level drive signals which are input to one or more loudspeakers. More elaborate signal processing devices are also used which can convert vibration signals produced by an impacting drumstick into sounds.
In addition to the transducers and electronic signal conditioning or signal processing devices which are presently available for use with acoustic drums, there are available a variety of electronic drum simulators. These devices essentially do away with the requirement for the shells or other acoustically resonant parts of acoustic drums, and require only a thin transducer pad which is struck by drumsticks, hands, or other objects. The transducer pads contain transducers which convert impact forces, pressure, or vibrations into electrical signals that vary in amplitude and frequency proportionally to the impact forces. The electrical signals are input to a signal processing unit which usually includes an audio amplifier which has user-controllable variable gain and has an output power lever sufficient to drive headphones or loudspeakers. Usually, the signal processing units of portable electronic drumheads include electronic wave fillers having frequency response characteristics which are also adjustable by a user.
Portable electronic drumheads of the type described above are useable both in musical performances, and for practice by a drummer, who may use earphones plugged into an earphone output of the signal processing unit to enable the drummer to practice in quiet environments without disturbing others.
In view of the advantages afforded by electronic accessories and replacements for purely acoustic drums as described above, Eventoff and DeCiutis, two of the three co-inventors of the present invention, disclosed a ‘Hybrid Drum” in U.S. patent application Ser. No. 12/910,524 filed Oct. 22, 2010, published on Apr. 26, 2012 as US 2012/0097009. The Eventoff application discloses a replacement drumhead for conventional acoustic drums, the drumhead having multiple layers including a first upper layer having an electrically conductive lower surface, a second layer having an electrically conductive upper surface, and a third, Force Sensing Resistor (FSR) resistor layer which is located between the first and second layers and has an electrical resistance which varies with force or impact pressure on the upper surface of the first, upper layer. According to the invention, a pair of electrically conductive strips arranged in an interdigitated spiral or concentric pattern is deposited on one or both of the inner facing surfaces of the upper and lower layers. The two conductors have a pair of leads which extend radially outwards from the outer circumferential edge of the drumhead, where they are electrically conductively coupled to input terminal pair of an input port of an electronic signal processing unit. According to the disclosure of Eventoff, the multi-layer drumhead is positioned on the open head of a drum shell, and clamped in tension on the open upper end of the shell in a conventional fashion. A tail containing the electrode leads extends radially outwards and downwards from the outer circumferential edge of the drumhead to an electronic signal processing box which is attached to the outer cylindrical wall surface of the drum shell.
The material composition of the upper and lower layers of the drumhead in Eventoff are not disclosed. However, since the tension required in drum heads is quire substantial, the upper and lower layers must be made of a relatively high strength material, such as a polyester or PET. Such materials can not only resist breakage under the high tensions required for drums, but also can stretch in response to tension without breaking. The Hybrid Drumhead disclosed in Eventoff affords significant advantages over prior art electronic drums which use piezoelectric acoustic transducers, because the FSR layer is an integral, internal part of the drumhead. Thus, the Hybrid Drumhead disclosed in Eventoff responds only to impacts on the drumhead, and is therefore insensitive to extraneous vibrations or sounds which can cause false triggering of electronic signal processing circuitry which receives input from an acoustic transducer. Moreover, since the FSR sensor layer of Eventoff is distributed over the entire playing surface of the drumhead, the drumhead is uniformly responsive to drumstick impacts over the entire drumhead. However, a need remained for a portable electronic drumhead which possessed advantages of the Hybrid Drumhead described in Eveloff, but did not require a drum body. That need was a motivating factor for the present invention.